"I've always overworked in the weight room. I love working with weights. I knew they'd give me the strength I need."
-Florence Griffith Joyner
Dumbbells and barbells. What's the difference? Which is better? Is the dress yellow or blue?
Both are awesome implements for weight training and should be staples in any weight lifting program.
Bodyweight movements are nice additions, but free weights should serve as the backbone of your lifting routines.
Although dumbbells and barbells are similar in their effects on muscle building, they have distinct advantages.
Dumbbells are fantastic for beefing up your forearms, which many gym rats are lacking in. In fact, some of you might not even need forearm isolation like Farmer Walks if you focus more on dumbbell work. Implementing these for both your pulling and pressing movements will also increase your grip strength, preventing your grip from being a limiting factor in movements like Pull-Ups.
In addition, dumbbells are great for correcting muscle imbalances. Barbell movements are more stable and might have one side overcompensating for the other. Dumbbell movements eliminate this discrepancy; when one arm starts to fatigue during your repetition, bring the other one down and finish your set.
Furthermore, dumbbells eliminate the need for a spotter in many cases. During the bench press, you can drop the dumbbells instead of relying on someone to hoist the barbell back to the rack. Dumbbell Overhead Press, if done correctly, will require nothing more than kicking your legs up to get your arms in proper position.
So what's the point of using barbell movements?
Some movements cannot be safely replicated with dumbbells. Deadlifts, for example, should only be done with barbells. Pulling dumbbells requires you to bend VERY close to the floor, similar to the depth on a deficit deadlift. This movement has its place, but most people lack the flexibility to do it well. Plus, you will eventually run out of heavy enough dumbbells to use in your deadlift workouts; most gyms don't carry dumbbells heavier than 150 lbs, which will be problematic once you can do reps with 315 on the barbell.
On another note, if your gym doesn't carry any dumbbells over 80 lbs, find a new gym; I've seen places like this before; it's a little depressing honestly.
Regarding heavy lifting, barbells are definitely safer when testing your strength limits. If you want to test your 5-rep-max on a barbell, you can adjust the weight in 5 lb increments. Moderate and heavy dumbbells, however, increase by 5 lbs EACH; you might miscalculate your 5-rep-max and fail to do even one rep (which is asking for an injury).
Barbells might also fatigue you less quickly than dumbbell movements. A heavy set of Dumbbell Bench Press sometimes leaves me winded for 3 minutes whereas benching the bar has nowhere near this effect. This is something to keep in mind if you're trying to condense your time spent in the gym.
Wrapping It Up
Dumbbells and barbells both have their place in any training program. Combine them with bodyweight movements to have an effective lifting routine.
For more distinction on these two, here's a fantastic article by strength coach Mark Rippetoe.